SessionStateService.cs

using System.Runtime.InteropServices;

namespace BatteryDown;

internal static class SessionStateService
{
    private const uint InvalidSessionId = 0xFFFFFFFF;
    private const int WtsSessionInfoEx = 25;
    private const int SessionLocked = 0;
    private static readonly IntPtr WtsCurrentServerHandle = IntPtr.Zero;

    public static bool IsLocked
    {
        get
        {
            var sessionId = WTSGetActiveConsoleSessionId();
            if (sessionId == InvalidSessionId)
            {
                return true;
            }

            if (!WTSQuerySessionInformation(
                    WtsCurrentServerHandle,
                    sessionId,
                    WtsSessionInfoEx,
                    out var buffer,
                    out _))
            {
                throw new InvalidOperationException("无法读取当前 Windows 会话状态。");
            }

            try
            {
                var info = Marshal.PtrToStructure<WtsInfoEx>(buffer);
                return info.Level == 1 && info.Data.SessionFlags == SessionLocked;
            }
            finally
            {
                WTSFreeMemory(buffer);
            }
        }
    }

    [DllImport("kernel32.dll")]
    private static extern uint WTSGetActiveConsoleSessionId();

    [DllImport("wtsapi32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool WTSQuerySessionInformation(
        IntPtr serverHandle,
        uint sessionId,
        int infoClass,
        out IntPtr buffer,
        out uint bytesReturned);

    [DllImport("wtsapi32.dll")]
    private static extern void WTSFreeMemory(IntPtr memory);

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct WtsInfoEx
    {
        public int Level;
        public WtsInfoExLevel1 Data;
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct WtsInfoExLevel1
    {
        public int SessionId;
        public int SessionState;
        public int SessionFlags;

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 33)]
        public string WinStationName;

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 21)]
        public string UserName;

        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 18)]
        public string DomainName;

        public long LogonTime;
        public long ConnectTime;
        public long DisconnectTime;
        public long LastInputTime;
        public long CurrentTime;
        public int IncomingBytes;
        public int OutgoingBytes;
        public int IncomingFrames;
        public int OutgoingFrames;
        public int IncomingCompressedBytes;
        public int OutgoingCompressedBytes;
    }
}